A thermosensitive recording medium is produced by the following way. A colorless or pale colored basic leuco dye (hereinafter referred to as “dye”) and an electron accepting color developing agent (hereinafter referred to as “developing agent”) such as phenolic compound are grinded and dispersed separately to form these fine particles dispersions, then these dispersions are mixed together, and a binder, a filler, a sensitizer, a slipping agent and other additives are added to produce a coating solution. Then a substrate, such as paper, synthetic paper, film or plastic, is coated with the coating solution to produce a thermosensitive recording medium. When the thermosensitive recording medium is heated by a thermal head, a hot stamp, a thermal pen or laser light and others, a recording image can be obtained by color formation owing to instant chemical reaction caused by heating. The thermosensitive recording medium is widely used not only for a terminal printer of facsimile or computer, an automatic ticket vending with the diversification of users, or a recorder for measuring instruments, but also for various tickets, receipts, labels, auto teller machines of banks, bills for gas and electricity, cash vouchers such as motorcycle-race and betting tickets and others.
However, since dyes and developing agents contained in a thermosensitive recording layer can be easily dissolved in various solvents, the thermosensitive recording medium has problems concerning storage stability such as color formation on the blanc area and reduction in level of formed color on contacting with plasticizer contained in ink (aqueous or oily) or adhesives. Furthermore, stamping ability as well as storage stability is required for business forms for delivery, bills, receipts and the like.
As a means to improve storage stability of image area, it is well know to form a protecting layer on a thermosensitive recording layer. Other means to improve storage stability of image area include using a specific developing agent and a specific stabilizer (References 1 and 2) and using the combination of a specific sensitizer with a specific stabilizer (Reference 3).
In contrast, powdered cellulose used in the present invention is prepared by hydrolyzing cellulose fiber such as pulp, followed by dry grinding to fine particles at ambient temperature, and is used to purification of foods etc. (Reference 4) because of its absorbing ability of organic solvents and the like.    Reference 1: Japanese Patent Application Public Disclosure No. 2003-154760    Reference 2: Japanese Patent Application Public Disclosure No. 2001-347757    Reference 3: International Publication WO2004/002748    Reference 4: Japanese Patent No. 3790648